The present invention relates to a beam diaphragm and an X-ray imaging apparatus. Particularly, the present invention is concerned with a beam diaphragm for radiating X-rays emitted from an X-ray source to a subject through apertures, as well as an X-ray imaging apparatus provided with the beam diaphragm.
In an X-ray imaging apparatus, X-rays emitted from an X-ray source are radiated to a subject through apertures of a beam diaphragm. The beam diaphragm includes two control rings having apertures of a common axis and being opposed to each other axially through a spacing and rotatable independently of each other, a blade positioned between the two control rings, and position adjusting means which causes the blade to move toward or away from the axis of the apertures in accordance with a difference in rotation between the two control rings (see, for example, Patent Literature 1).
[Patent Literature 1]
U.S. Pat. No. 5,689,544 (Columns 3 to 5, FIGS. 1 and 2)
In the above beam diaphragm, the degree of opening of each aperture decreases when the blade is moved toward the axis of the apertures, and increases when the blade is moved away from the aperture axis.
Therefore, the degree of opening of each aperture becomes maximum when the blade is moved remotest from the axis of the apertures. It is desirable that a maximum value of aperture opening be as large as possible under a limited profile dimension of the beam diaphragm.